As one of authentication methods used in a biometric authentication technology, there is known “one-to-N authentication” in which authentication is performed by matching biometric information input by a user against biometric information on N persons registered in advance. When one-to-N authentication is used, because the biometric information input by a user is matched against biometric information on N persons registered in advance, it takes a long time to output the authentication result as the number of registered persons N related to the biometric information is increased. An example of a technology in use that reduces a time taken to perform authentication includes a narrow down technology that classifies registration data and that selects, as target data for the matching, registration data that belongs to the same classification as that of the input data when matching the registration data.
Patent Document 1: Japanese Laid-open Patent Publication No. 03-260778
Patent Document 2: Japanese Laid-open Patent Publication No. 2006-244365
However, with the related technology described above, there is a problem in that the accuracy of narrow down data is unstable as described below.
Namely, the quality of the biometric information that is acquired when registration and authentication is performed may vary depending on a method of inputting a portion used for the authentication and, furthermore, depending on an external factor, such as a stain attached to the portion used for the authentication or a stain attached to a reading device. Accordingly, even if biometric information on the same person is classified, the biometric information that is acquired at the time of authentication is not always classified into the same classification as that of the biometric information that is acquired at the time of registration. As described above, if the biometric information on the same person is classified into a different classification, because the target biometric information is not narrowed down to the biometric information that is used for the matching, the same person may possibly and erroneously be determined to be a different person.